Paint strippers are important industrial chemicals, and are used both in the finishing and refinishing of manufactured articles and in the clean-up of painting facilities. Large amounts of paint-stripping compositions are used in connection with the refinishing of commercial and military aircraft, as well as in the manufacture of motor vehicles.
A threshold requirement for a good paint-stripping composition is that it efficiently and effectively remove a variety of paints without harming the underlying workpiece. This requirement is particularly important in connection with the aircraft industry, since aircraft are frequently fabricated from aluminum or magnesium based alloys which are easily corroded by acidic or alkaline materials.
It is also most important that paint-stripping compositions be of relatively low toxicity. There is an ever growing concern about the release of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) into the atmosphere, because such compounds can be toxic to plant and animal life, and impose serious problems of atmospheric pollution. As a consequence, governmental regulations have strictly curtailed the amounts of VOCs and HAPs which an industry can release. As a consequence, industry must avoid the use of volatile organic compounds, or install expensive recovery systems. Since paint-stripping compositions are typically employed in large volumes, and distributed over relatively large areas, the escape of VOCs and HAPs therefrom can be significant. As a consequence, there is need for paint-stripping compositions which have a low content of volatile and/or hazardous organic compounds. Finally, since cost is always a significant concern with regard to chemicals such as paint-strippers which are used in large volumes, there is a need for a low-cost stripping composition which meets the foregoing criteria.
The foregoing requirements are often mutually exclusive, making it difficult for industry to develop paint-strippers which are highly effective against a broad spectrum of paints, that do not corrode relatively reactive aircraft alloys, and which are low in toxicity, low in cost, and have a low concentration of volatile and/or hazardous organic compounds. Caustic materials such as inorganic alkalis are highly effective for removing a variety of paints, but are also highly corrosive to many alloys, in addition to being dangerous and toxic. Organic compounds such as phenols are quite effective strippers for a variety of paints, and are generally non-corrosive, but these materials are highly toxic, and relatively expensive. Solvents such as benzene, toluene, and halocarbons are effective strippers for many commonly employed paints, but such materials are highly volatile, and in some instances, toxic and/or flammable.
A number of paint-stripping compositions are known in the prior art. For example, U.S. Pat. No. 5,454,985 discloses paint-stripping compositions based upon a mixture of benzyl alcohol and water, which compositions may also include acidic or alkaline accelerators. U.S. patent application Ser. No. 08/610,155 discloses paint strippers based upon benzyl alcohol and water which further include peroxide activators. U.S. Pat. No. 3,355,385 discloses paint-stripping compositions based upon aqueous hydrogen peroxide in combination with various organic solvents, including methylene chloride, and other halocarbons. U.S. Pat. Nos. 5,518,661 and 4,445,939 both show paint-stripping compositions based upon specific mixtures of benzyl alcohol and methylene chloride. As can be seen, the prior art has made many attempts at fabricating paint-stripping compositions, but to date, there is still a need for a highly effective, non-corrosive, low-toxicity paint-stripping composition having a low concentration of VOCs and HAPs.
In accord with the present invention, and as will be explained in greater detail hereinbelow, it has been found that paint-stripping compositions which are highly effective against a variety of paint formulations, and which are capable of operating at a neutral or near neutral pH (typically in the range of 4-8) can be prepared so as to include a relatively small amount of VOC or HAP materials therein. These and other advantages of the present invention will be apparent from the discussion, description and examples which follow.